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<h1 id="Checker_Framework_developer_manual">Checker Framework developer manual</h1>

<p>
  If you wish to use the Checker Framework, see its user manual
  (<a href="https://checkerframework.org/manual/">HTML</a>,
  <a href="https://checkerframework.org/manual/checker-framework-manual.pdf">PDF</a>).
</p>

<p>
This document contains information for Checker Framework developers,
including people who wish to edit its source code or make pull requests.
</p>

<p>Contents:</p>
<!-- start toc.  do not edit; run html-update-toc instead -->
    <ul>
      <li><a href="#building-from-source">Building the Checker Framework from source</a></li>
      <li><a href="#Directory_structure">Directory structure</a>
        <ul>
          <li><a href="#Related_repositories">Related repositories</a></li>
        </ul></li>
      <li><a href="#Build_tasks">Build tasks</a></li>
      <li><a href="#tests">Testing the Checker Framework</a>
        <ul>
          <li><a href="#testing-optimizations">Testing optimizations</a></li>
        </ul></li>
      <li><a href="#code-style">Code style</a></li>
      <li><a href="#IDE_configuration">IDE configuration</a></li>
      <li><a href="#pull-requests">Pull requests</a>
        <ul>
          <li><a href="#pull-requests-branches">Branches</a></li>
          <li><a href="#pull-requests-maintainers">Pull request and commit notes for maintainers</a></li>
        </ul></li>
      <li><a href="#github-configuration">GitHub configuration</a></li>
      <li><a href="#ci">Continuous Integration</a>
        <ul>
          <li><a href="#ci-azure-pipelines">Azure Pipelines</a>
            <ul>
              <li><a href="#ci-increasing-quota">Increasing quota</a></li>
              <li><a href="#project-visibility">How to change project visibility settings</a></li>
            </ul></li>
          <li><a href="#ci-travis">Travis CI</a></li>
          <li><a href="#ci-failure">Reproducing Continuous Integration build failures</a></li>
        </ul></li>
      <li><a href="#Documenting_refactoring_ideas">Documenting refactoring ideas</a></li>
      <li><a href="#annotated-library-version-numbers">Version numbers for annotated libraries</a></li>
      <li><a href="#Making_a_Checker_Framework_release">Making a Checker Framework release</a></li>
      <li><a href="#Supporting_a_new_version_of_Java">Supporting a new version of Java</a></li>
      <li><a href="#Case_studies">Describing a case study</a></li>
      <li><a href="#Counting_annotations">Counting annotations</a></li>
      <li><a href="#Build_historical">Building a historical version of the Checker Framework</a></li>
    </ul>
<!-- end toc -->


<h2 id="building-from-source">Building the Checker Framework from source</h2>

<p>
See section <a href="https://checkerframework.org/manual/#build-source">Building
from source</a> in the Checker Framework manual.
</p>


<h2 id="Directory_structure">Directory structure</h2>

<p>
The <a href="https://github.com/typetools/checker-framework">checker-framework
repository</a> contains several related projects:
</p>

<dl>
  <dt><code>framework</code></dt>
  <dd>the framework that enables building pluggable type checkers</dd>

  <dt><code>checker</code></dt>
  <dd>the type checkers provided with the Checker Framework</dd>

  <dt><code>javacutil</code></dt>
  <dd>utilities for integrating with javac</dd>

  <dt><code>dataflow</code></dt>
  <dd>a dataflow framework that is used by the Checker Framework, <a href="https://errorprone.info">Error Prone</a>, <a href="https://github.com/uber/NullAway">NullAway</a>, and other tools</dd>
</dl>

<p>
The repository also contains the following directories:
</p>
<dl>
  <dt><code>docs</code></dt>
  <dd>documentation: manual, tutorial, examples, developer docs</dd>
</dl>


<h3 id="Related_repositories">Related repositories</h3>

<p>
  The <a href="https://github.com/typetools/checker-framework"><code>checker-framework</code></a> project
  depends on
  the <a href="https://github.com/typetools/jdk"><code>typetools/jdk</code></a> project
  and the <a href="https://github.com/typetools/stubparser"><code>stubparser</code></a> project.
When making changes to one of these projects, you may also need to make changes to one or more of the others.
</p>

<p>
If you make related changes in the <code>checker-framework</code> and <code>jdk</code>
repositories, use the <em>same
branch name</em> for each.  The continuous integration framework will find
and use that branch when running tests.
For example, when continuous integration runs for branch <em>B</em> of fork <em>F</em> of <code>checker-framework</code>, it will use branch <em>B</em> of fork <em>F</em> of the other repositories (if they exist).
The same is true for the other projects.
</p>

<p>
You do not need to explicitly build the <code>jdk</code> repository.  Building
the Checker Framework (say, via <code>./gradlew assemble</code>) automatically
makes the Checker Framework use the annotated JDK that exists
at <code>../jdk/</code> &mdash; that is, as a sibling directory of the Checker
Framework named <code>jdk</code>.
</p>

<p>
If a change spans multiple projects, make pull requests for all of them.
Each pull request description's should link to all the others.
</p>

<p>
Furthermore, whenever you make a pull request from
a <code>checker-framework</code> branch A into branch B, if B has a
corresponding <code>jdk</code>
branch, then A also needs one.
A needs the branch even if A's branch is identical to B's; in that case,
beware of a <a href="#azure-pipelines-bug-same-commit-hash">bug in Azure Pipelines</a>.
</p>


<h2 id="Build_tasks">Build tasks</h2>

<p>
Full instructions for building the Checker Framework from sources appear in
the <a href="https://checkerframework.org/manual/#build-source">Checker
Framework manual</a>. This section describes the build system (the Gradle build tasks).
</p>

<p>
Don't run the <code>gradle</code> command, which would use whatever version
of Gradle is installed on your computer.  Instead, use
the <code>gradlew</code> script in the <code>checker-framework</code>
directory, also known as
the <a href="https://docs.gradle.org/current/userguide/gradle_wrapper.html">Gradle
wrapper</a>.
</p>

<p>
Frequently-used tasks:
</p>
<ul>
  <li> <code>assemble</code>: builds all artifacts, including jars and Javadoc jars.
  <li> <code>assembleForJavac</code>: builds only the jars required to use <code>checker/bin/javac</code>; faster than <code>assemble</code>.
  <li> <code>build</code>: <code>assemble</code>, plus runs all JUnit tests.
  <li> <code>allTests</code>: runs all tests.
  <li> <code>spotlessApply</code>: reformats Java files.
  <li> <code>spotlessCheck</code>: checks formatting of Java files.
  <li> <code><em>NameOfJUnitTest</em></code>: runs the JUnit test with that name; for example, <code>NullnessTest</code>.
  <li> <code>task</code>: lists tasks; use <code>--all</code> to see all tasks.
</ul>

<p>
If you run a task from the main directory, then it will run that task in all
subprojects with a task by that name. So, if you run <code>./gradlew
allTests</code> that runs all tests everywhere. But <code>(cd
framework &amp;&amp; ../gradlew allTests)</code> only runs tests in
the <code>framework</code> project.
Alternatively, running <code>:framework:allTests</code> from the
main directory or any subproject runs the <code>allTests</code> task only in the <code>framework</code> project.
</p>

<p>
An iterative build-test-debug cycle where you assemble the Checker Framework
and execute its tests can sometimes lead to a state where Gradle is not able to
compile and build the system for no obvious reason.
This is especially common when you kill tests before they fully finish, or kill
compilation before it is fully complete, leading to a bad state or an
inconsistent build cache.
</p>

<p>
Below are some steps you might try to resolve this issue (in order):
</p>
<ul>
  <li><code>./gradlew --no-build-cache assemble</code>: attempts to rebuild the Checker Framework without the build cache.
  <li>Kill any Gradle daemons; run <code>./gradlew --status</code> to get a list of pids for Gradle.
  <li><code>git clean -fdx</code>: removes all files that are not under version control. <b>Add or stash files that you would like to
      keep before running this command</b>.
  <li>Delete the Gradle build cache, usually located at <code>~/.gradle/caches</code>. Note: this will delete the entire build
      cache, including the cache for other Gradle projects on your machine; the build step for the Checker Framework will need to re-download all required dependencies.
</ul>

<h2 id="tests">Testing the Checker Framework</h2>

<p>
For writing new test cases, see file <a href="https://raw.githubusercontent.com/typetools/checker-framework/master/checker/tests/README.md"><code>checker/tests/README.md</code></a>.
</p>


<h3 id="testing-optimizations">Testing optimizations</h3>

<p>
To test an optimization that should speed up type-checking, see
the <code>test-daikon-part<em>N</em>.sh</code> stage of the <code>daikon_part<em>N</em>_jdk*</code> job
of the Azure Pipelines CI job.  Compare the run time of this stage (or of
the entire <code>daikon_jdk*</code> job) between the master branch and a
branch with your improvements.
</p>

<p>
You can also compare run times of the Checker Framework test suite.
</p>


<h2 id="code-style">Code style</h2>

<p>
Code in this project follows the
<a href="https://google.github.io/styleguide/javaguide.html">Google Java Style
  Guide</a>,
<a href="https://homes.cs.washington.edu/~mernst/advice/coding-style.html">Michael
Ernst's coding style guidelines</a>, and <a href="https://www.oracle.com/java/technologies/javase/codeconventions-indentation.html#248">Oracle's
Java code conventions</a>.
</p>

<p>
From the command line, you can format your code by running <code>./gradlew spotlessApply</code>.
You
can <a href="https://github.com/google/google-java-format#using-the-formatter">configure
your IDE</a> (Eclipse or IntelliJ) to use the formatting.
</p>

<p>
We don't use <code>@author</code> Javadoc tags in code files.
Doing so clutters the code, and is misleading once that individual
is no longer maintaining the code.
Authorship (and who has made changes recently) can be obtained from the
version control system, such as by running <code>git annotate <em>filename</em></code>.
</p>

<p>
  Every class, method, and field (even private ones) must have a
  descriptive Javadoc comment.
</p>

<p>
If a nested class has a very common and generic name, do
not <code>import</code> it.  In code, write the outer and inner class name
(as in <code>Tree.Kind</code> or <code>Map.Entry</code>) rather than just
the simple name <code>Kind</code> or <code>Entry</code>.
</p>


<h2 id="IDE_configuration">IDE configuration</h2>

<p>
First clone and build all projects from their sources, from the command line,
using the instructions
at <a href="https://checkerframework.org/manual/#build-source">https://checkerframework.org/manual/#build-source</a>.
After that succeeds, import the projects into your IDE as Gradle projects.
</p>

<p>
If your IDE cannot find <code>com.sun.source.*</code> packages, try changing the project JDK to JDK 11 or JDK 17.
</p>

<p>
For VS Code and Eclipse, run <code>./gradlew eclipseClasspath</code> before running
the IDE for the first time.
This ensures generated files are not put in the standard <code>../bin/</code> directories.
</p>

<p>
For VS Code and Eclipse, run <code>./gradlew eclipseClasspath</code> before running
the IDE for the first time.
This ensures generated files are not put in the standard <code>../bin/</code> directories.
</p>


<h2 id="pull-requests">Pull requests</h2>

<p>
Each pull request should address a single concern, rather than (say)
addressing multiple concerns such as fixing a bug, adding a feature, <em>and</em>
changing formatting.  Focusing each pull request on a single concern makes
the commit easier to understand and review.  It also makes the commit
history (after the pull request is merged) easier to understand and (if
necessary) revert.
</p>

<p>
The pull request title should clearly explain the change.  It will be used
as the commit message for your change.  If the pull request fixes an issue
in the issue tracker, its title should end with "; fixes #NNN" where NNN is
the fixed issue.
</p>

<p>
  Your pull request (whether it is a bug fix or a new feature) should
  include tests that fail before your change and pass afterward.
</p>

<p>
If you make a user-visible change, update the manual (or add a new section)
and add a brief description at the top of the changelog
(file <code>docs/CHANGELOG.md</code>).
</p>

<p>
To reduce iterations of code review, please follow
the <a href="#code-style">coding conventions</a>.
Also enable <a href="#ci">continuous integration</a> on your fork of the Checker
Framework and ensure that it passes before you open a pull request.
</p>

<p>
A pull request marked as "draft" means it should not be reviewed.  To use a
"draft" pull request for discussions, make it in a fork.  If it were in
the <code>typetools</code> GitHub organization, it would use CI resources
and thus slow down CI feedback for other pull requests.
</p>

<p>
Also
see <a href="https://homes.cs.washington.edu/~mernst/advice/github-pull-request.html">Michael
Ernst's advice about creating GitHub pull requests</a>.
</p>


<h3 id="pull-requests-branches">Branches</h3>

<p>
  It is good style to create a branch (in your fork of the Checker
  Framework GitHub repository) for each independent change.
  Do not make changes to your <code>master</code> branch.
  If you have write access to the <code>typetools</code> repository, don't
  work in a branch of it, because such a branch competes for CI resources
  with all pull requests.
</p>

<p>
  You may need to make changes to multiple repositories.
  See <a href="#Related_repositories">"Related repositories"</a> above.
</p>

<p id="azure-pipelines-bug-same-commit-hash">
Azure Pipelines has a bug:  whenever two CI jobs would run code with the same
commit hash, it re-uses a previous execution result.  This is a bug because the
CI job's behavior may depend on the branch name and other factors that are
independent of the commit hash.  This means that you may see spurious successes
or failures when your branch of (say) the <code>jdk</code> repository has the
identical commit hash to some other branch that Azure Pipelines previous ran a
job for.
</p>


<h3 id="pull-requests-maintainers">Pull request and commit notes for maintainers</h3>

<p>
It is acceptable to commit small, noncontroversial changes directly to
master.  (This policy differs from some projects, which require an issue
tracker issue and a pull request for every change, however minor.)
As with pull requests, each commit should address a single concern.
For any change where you want feedback, or where others might have
useful comments or might disagree, please submit a pull request.  Be
conservative in your judgment; others might consider something
controversial that you do not.
</p>

<p>
Try to review pull requests promptly, to avoid stalling others while
waiting for your feedback.  If you have been waiting for more than a week
after the pull request was assigned with no feedback, then ping the
assignee, wait at least another business day, and then go ahead and push
your changes.  It's great if reviewers can give feedback, but if they are
too busy to do so, you should recognize that and move on.
</p>


<h2 id="github-configuration">GitHub configuration</h2>

<p>
When you installed Git, you should have set your name and email address.  If you have not yet done so, do it now:
</p>
<pre>
git config --global user.name "<em>FIRST_NAME LAST_NAME</em>"
git config --global user.email "<em>USERNAME</em>@<em>SOMEDOMAIN.COM</em>"
</pre>

<p>
Before you make any commits (even to your own fork),
update your GitHub account profile so it contains your complete name.
This is necessary to include you in
the <a href="https://checkerframework.org/manual/#credits">list of
contributors</a>.
</p>

<p>
You will want your own GitHub fork of any project you plan to modify.  We
recommend that, for each fork, you configure GitHub
to <a href="https://docs.github.com/en/repositories/configuring-branches-and-merges-in-your-repository/configuring-pull-request-merges/managing-the-automatic-deletion-of-branches">delete
branches after they are merged</a>.
</p>


<h2 id="ci">Continuous Integration</h2>

<p>
The Checker Framework has continuous integration jobs that run in Azure
Pipelines, CircleCI, and/or Travis CI on each push to GitHub.
We recommend Azure Pipelines.
</p>

<h3 id="ci-azure-pipelines">Azure Pipelines</h3>

<p>
  To enable Azure Pipelines continuous integration for your fork:
  (This is a summary of the <a href="https://learn.microsoft.com/en-us/azure/devops/pipelines/create-first-pipeline?view=azure-devops">Azure
  Pipelines getting started directions</a>.)
</p>
<ul>
  <li>Browse to <a href="https://dev.azure.com/">dev.azure.com</a>.
      (You might need to create a (free) account.)</li>
  <li>Click "Create a project to get started" and enter an appropriate name</li>
  <li>Click "public".
    <ul>
      <li>If this option is not available, create the project and <a href="#project-visibility">modify its visibility</a> later.</li>
    </ul>
  </li>
  <li>(You might have to wait a few days for your project to be created.)
  <li>Click "create project"</li>
  <li>At the left, click the blue rocket labeled "pipelines"</li>
  <li>Click "new pipeline"</li>
  <li>Click "GitHub"
      (You might need to authorize the app on GitHub.)</li>
  <li>Click "Select a repository"</li>
  <li>Choose <em>MYUSERID</em>/checker-framework</li>
  <li>Choose the default radio button, "only selected repositories".  <b>Do not</b> choose "all repositories".</li>
  <li>Choose "Existing Azure Pipelines YAML file"</li>
  <li>Select "/azure-pipelines.yml" in the dropdown menu</li>
  <li>Approve and install.</li>
  <li>Click "run".</li>
</ul>

<h4 id="ci-increasing-quota">Increasing quota</h4>

<p>
By default, your project has no parallelism and thus pipeline runs fail
immediately. Azure DevOps provides
a <a href="https://aka.ms/azpipelines-parallelism-request">Microsoft Forms</a>
through which you can request increased public project concurrency for validated
open-source projects.
</p>

<p>
It may be the case that you obtain only 1800 minutes per month, only one
parallel job at a time, and only for private projects.  In this case, you need
to ask Azure to lift all three restrictions.  Send mail such as the following:
</p>

<p>
  Thank you for granting me free tier access to Azure Pipelines.
  I am working on the open-source <a href="https://github.com/typetools/checker-framework">Checker Framework</a>.
  Therefore could you please make the following changes, per the policies at https://azure.microsoft.com/en-us/products/devops/pipelines/?
</p>
  <ul>
    <li>Increase parallelism beyond 1 job.</li>
    <li>Increase time limit beyond 1800 minutes per month.</li>
    <li>Permit the project to be public, for collaboration.</li>
  </ul>
<p>
  Thanks for your help.
</p>


<h4 id="project-visibility">How to change project visibility settings</h4>

<p>
To change your project's visibility settings (usually to "Public" to enable CI):
</p>

<ul>
  <li>Browse to your project on <a href="https://dev.azure.com">dev.azure.com</a>.</li>
  <li>Click the "Project Settings" button.</li>
  <li>Click the "Visibility" dropdown.</li>
  <li>Click "Public".</li>
</ul>


<h3 id="ci-travis">Travis CI</h3>

<p>
  To enable Travis CI continuous integration for your fork:
</p>
<ul>
  <li>Browse to <a href="https://www.travis-ci.com/">travis-ci.com</a></li>
  <li>Click the downarrow for the dropdown, near your face in the upper right corner</li>
  <li>Click settings</li>
  <li>Find "checker-framework" in the list, and click the slider to enable it.</li>
</ul>


<h3 id="ci-failure">Reproducing Continuous Integration build failures</h3>

<p>
If a CI job fails, examine the CI logs.
</p>

<p>
You can also run the same test locally.  Each CI job runs a different command.
You can see the commands in
file <a href="https://github.com/typetools/checker-framework/blob/master/azure-pipelines.yml"><code>azure-pipelines.yml</code></a>,
usually on lines starting with <code>bash:</code>.  The scripts that are run
generally just invoke gradle to run particular tasks.
</p>

<p>
Sometimes, CI tests for your pull request may fail even though the same command
passed locally.  First, ensure you are using the same JDK.  Second, all CI tests
are run in a Docker container, and you can use that container if necessary.  The
container names are in top-level
file <a href="https://github.com/typetools/checker-framework/blob/master/azure-pipelines.yml"><code>azure-pipelines.yml</code></a>,
on lines starting with <code>container:</code>.
</p>


<h2 id="Documenting_refactoring_ideas">Documenting refactoring ideas</h2>

<p>
Don't open issues for code improvement ideas (such as potential refactorings).
If it can be described concisely and is unlikely to be rediscovered by other
people, write a TODO comment in the code.  The code comment is more likely to be
noticed by someone
working with the code, and it is equally easy to search for.  Furthermore,
it doesn't clutter the issue tracker.  Clutter in the issue tracker reduces
morale, makes it harder to search, and makes the project appear
lower-quality than it actually is.
</p>


<h2 id="annotated-library-version-numbers">Version numbers for annotated libraries</h2>

<p>
  We maintain annotated versions of some third-party libraries.  The source
  code appears in a fork in
  the <a href="https://github.com/typetools">GitHub <code>typetools</code>
  organization</a>.  Binaries are hosted
  at <a href="https://central.sonatype.com/search?q=annotatedlib">Maven Central
  in the <code>org.checkerframework.annotatedlib</code> group</a>.
</p>

<p>
Annotated libraries should be based on a released version of the upstream
library, not an arbitrary commit in the upstream library's version control
system.  The library's version number is the same as the upstream version
number.
</p>

<p>
When making a new version of an annotated library, between upstream
releases, add ".0.1" to the end of the version number.  For example, if we
already uploaded version 6.2 to Maven Central, the next version we upload
would be 6.2.0.1.  This accommodates the possibility that the upstream
maintainers release 6.2.1.  Our further releases increment the last number,
for example to 6.2.0.2.
</p>


<h2 id="Making_a_Checker_Framework_release">Making a Checker Framework release</h2>

<p>
See a separate document about the Checker Framework release process:
<a href="https://htmlpreview.github.io/?https://github.com/typetools/checker-framework/master/docs/developer/release/README-release-process.html">web version (from previous release)</a> or
<!-- This relative URL works from a clone, but not from the web. -->
<a href="release/README-release-process.html">local version (link works from a clone)</a>.
</p>


<h2 id="Supporting_a_new_version_of_Java">Supporting a new version of Java</h2>

<p>
To upgrade the Checker Framework to use a newer version of Java:
</p>

<pre>
# Create a branch named "java-23".
cd $t/checker-framework-fork-mernst-branch-master
gnb java-23
cd $t/checker-framework-fork-mernst-branch-java-23

# Edit:
checker/bin/wpi.sh
checker/bin/wpi-many.sh (diff it against wpi.sh)
# Rename and edit:
checker/bin-devel/Dockerfile-ubuntu-jdkXX
checker/bin-devel/Dockerfile-ubuntu-jdkXX-plus (diff it against Dockerfile-ubuntu-jdkXX)
# Further search for: (java|jdk).?23\b
# Don't push changes yet.

# Use the latest version of Gradle, which supports the new JDK version
# (see https://docs.gradle.org/current/userguide/compatibility.html):
for wmtest in wpi-many-tests-bcel-util wpi-many-tests-bibtex-clean wpi-many-tests-ensures-called-methods wpi-many-tests-html-pretty-print wpi-many-tests-owning-field -wpi-many-tests-bibtex-clean ; do
  cd $t/$wmtest && \
  (./gradlew wrapper --gradle-version 8.10 && ./gradlew build --warning-mode=all) && \
  git commit -m "Use Gradle 8.10" gradle/wrapper/gradle-wrapper.properties && \
  git push
done
# Now update file checker/tests/wpi-many/testin.txt.

# Build the Docker images for the newest JDK version (others need not be rebuilt).

# Push changes.  Fix any build failures.
</pre>


<h2 id="Case_studies">Describing a case study</h2>

<p>
  After you have performed a case study of applying some checker to an
  open-source codebase, you should have:
</p>

<ul>
  <li>
    the unannotated code, as of the time/commit you started annotating it.
    This might be in your forked repository, or in an upstream repository.
  </li>
  <li>
    the annotated code.  Typically, this is in a branch of your forked repository.

    <p>
    In the annotated code, each <code>@SuppressWarnings</code> annotation should have a brief justification, explaining why the code is correct and the warning is a false positive.
    The justification should be a <code>//</code>-style comment, on the same line as the argument to <code>@SuppressWarnings</code>.  For example:
    </p>

<pre>
  @SuppressWarnings("nullness:assignment") // dynamic check: checked against null immediately above

  @SuppressWarnings({
    "nullness:assignment" // dynamic check: checked against null immediately above
  })
</pre>

    If there are more than about 10 warning suppressions, prefix each one by a
    category followed by a colon (as with "dynamic check:") above, to aid in
    computing statistics about the causes of false positive warnings.

  </li>
  <li>
    the command to run the type-checker(s) on the annotated code.
  </li>
  <li>
    a list of all the bugs you fixed, with a brief description of each.  The
    description can point to pull requests, or commits, or just be text; provide
    whatever is most helpful.
  </li>
</ul>


<h2 id="Counting_annotations">Counting annotations</h2>

<p>
After you have annotated a project, you may wish to count the annotations that you have written.
These programs will help you do that:
</p>

<ul>
  <li><a href="https://checkerframework.org/api/org/checkerframework/common/util/count/AnnotationStatistics.html">AnnotationStatistics</a></li>
  <li><a href="https://checkerframework.org/api/org/checkerframework/common/util/count/JavaCodeStatistics.html">JavaCodeStatistics</a></li>
  <li><a href="https://checkerframework.org/api/org/checkerframework/common/util/count/report/ReportChecker.html">ReportChecker</a></li>
  <li><a href="https://github.com/typetools/checker-framework/blob/master/checker/bin-devel/count-suppression-reasons">count-suppression-reasons</a></li>
</ul>


<h2 id="Build_historical">Building a historical version of the Checker Framework</h2>

<p>
The use of four different repositories, as explained in
"<a href="#Related_repositories">Related repositories</a>" above, means that you
cannot just check out an old version of the Checker Framework and build it
with <code>./gradlew assemble</code>.  By default, the Checker Framework build
uses the latest version of the other three repositories, which are rarely
compatible with an old version of the Checker Framework.  One symptom of the
problem is a "Can't find stubparser jar" error message.
</p>

<p>
To build an old version of the Checker Framework, you need to use old versions
of the other repositories as well.  Clone them into siblings of
the <code>checker-framework/</code> directory that holds your old version of the
Checker Framework.
</p>

<p>
Here are <b>general rules</b>:
If the Checker Framework version is a commit on branch B with date D, then use
the commits on other repositories' branch B (or <code>master</code>, if branch B
does not exist) that precede D.  (This isn't quite right, because the commits
may have been made earlier but all pushed at the same time, so you might need to
look at commits that are relatively soon after D.)  To obtain these, view the
GitHub history and click on the pull request to see the commits that were merged
into it.  You cannot obtain these from the Git history, because after a pull
request is merged, the commits in the pull request branch are squashed and the
branch is deleted.
</p>

<p>
  Here are <b>special cases</b>:
</p>
<ul>
  <li>
    If you are building an old <em>released</em> version of the Checker Framework,
    then <code>annotation-tools</code> should have a corresponding tag for the
    release.
  </li>
  <li>
    Recently, any Stubparser change that breaks building the Checker
    Framework, should have a new version number. So you should check out
    Stubparser to the commit that changed the version number (to what it is
    in <code>checker-framework/build.gradle</code>).
  </li>
</ul>

<p>
  The script <code>checker/bin-devel/checkout-historical.sh</code> approximates
  these rules.  It is able to build the Checker Framework back through at least
  mid-April 2019.  It cannot build the Checker Framework as of mid-January 2019.
</p>


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